The invention relates to paint color changers for paint application systems. More particularly, the invention concerns a powder paint color changer adapted for use with paint application systems utilizing solid particulate paint particles entrained in a fluid such as air.
Paint color changers are known in the art for both liquid and powder paint applications. In liquid paint applications, the color changers are positioned as closely as possible to the paint application apparatus to save on solvent and paint waste. For powder applications, it has been found better to place the color changers closer to the source of the powder paint rather than to the application device.
In the typical powder paint application, pressurized air is used as a diluter and carrier of the powder paint particles to the application device via a color changer. Unlike the liquid paint application, powder applications do not utilize cleaning solvents. The transport air is a neutral means of transporting the powder such that the powder paint is very diluted in the hoses connecting the various apparatus of the system, and its amount is relatively small. These characteristics are what suggest placing the powder color changer closer to the feed hoppers rather than as close as possible to the paint applicator as is the case for liquid paint applications. This feature helps to reduce the number and length of powder feeding hoses in a multiple color system.
In prior art powder paint color changers, such as those disclosed in U.S. Pat. No. 4,302,481 to Ribnitz, et al., where multiple colors enter a common color changing manifold, separate air purging channels are required for each manifold powder paint input. This complicates the color changing arrangement thereby adding expense.
Another problem with powder paint applications is the phenomenon known as impact fusion. Impact fusion occurs where the particles of powder paint encounter surfaces in prior art color change manifolds having relatively high friction surfaces thereby leading to powder particle agglomeration and adhesion to the color changer surfaces. Such adhesion, in turn, leads to problems in both cleaning of the apparatus prior to changing colors and may, over time, lead to inoperativeness of the color changer due to clogging of various passageways therein.
Therefore, there is a need in the art for a color changer for powder paint applications providing facile cleaning and resistance to particulate impact fusion at powder paint carrying surfaces therein.